Assembly of clothes dryers having improved safety controls



Nov. 14, 1961 F. H. RICHTERKESSING EIAL 3,008,699

ASSEMBLY OF CLOTHES DRYERS HAVING IMPROVED SAFETY CONTROLS Filed Dec. 31 1959 5 Sheets-Sheet l INVENTORS WALTER M ING LD G S S E K R n H m R H M m rr ATTORNEY 1961 F. H. RICHTERKESSING ETAL 3,008,699

ASSEMBLY OF CLOTHES DRYERS HAVING IMPROVED SAFETY CONTROLS 5 Sheets-Sheet 2 Filed Dec. 51, 1959 REMOVABLE. .LINT TRAY '23 ,139 lAccEs5 aaaz swrrcu INVENTORS WALTER M meou: FRANK H. RlCHTERKESSNG BY 1 .2. iwuhwk ATTORNEY Prim pEeATu 2i:

Nov. 14, 1961 F. H. RIICHTERKESSING EI'AL 3,008,699

ASSEMBLY OF CLOTHES DRYERS HAVING IMPROVED SAFETY CONTROLS Filed Dec. 51, 1959 5 Sheets-Sheet 3 INVENTORS WALTER M. mebu: FRANK H. RKZHTERKESSING BY v Wwwfi ORNEY Nov. 14, 1961 F. H. RICHTERKESSING ETAL 3,008,699

ASSEMBLY OF CLOTHES DRYERS HAVING IMPROVED SAFETY CONTROLS 5 Sheets-Sheet 4 Filed Dec. 51, 1959 INVENTORS W LE K R E \T w Mm N A WR Nov. 14, 1961 F. H. RICHTERKESSING ETAL 3,008,699

ASSEMBLY OF CLOTHES DRYERS HAVING IMPROVED SAFETY CONTROLS Filed Dec. 51, 1959 v 5 Sheets-Sheet 5 TEMPERATURE umu-rme THERMO- o5' STAT FOR mcomme HOT eAs 02 H7\ ACCESS poo Swrrc J39 I an 1 H7 m REMOVABLE 65 LJNT TRAY me THERMO s-rAT FOR v EXHAUST GAS INVENTOR WALTER M. INGOLD FRANK H. RKZHTERKESSWG BY E ATTORNEY Unit d Sta es I a n O ce 3,008,699 Patented Nov. 14, 1961 3,008,699 ASSEMBLY OF CLOTHES DRYERS HAVING IMPROVED SAFETY CONTROLS Frank H. Richterkessing and Walter M. Ingold, Louisville, Ky., assignors to W. M. Cissell Manufacturing Company, Louisville, Ky., a corporation of Kentucky Filed Dec. 31, 1959, Ser. No. 863,209 6 Claims. (Cl. 263-33) This invention relates to an assembly of a plurality of automatically controlled, independently operable, clothes dryers and more particularly to such an assembly useful in unattended, coin-meter control, dryer establishments.

In'such establishments, the building codes usually require a generous sized air inlet for each dryer and a vent conduit suitably related in size to the size of that inlet. However, for many reasons it is not economically practical to provide a separate Vent conduit for each dryer and, in general, the practice is to employ a common vent conduit of appreciable size for an entire battery of dryers. When such a single, large-size common vent conduit is used, there remains. the ever-present problem of blowback of pressure from one dryer to another through that common conduit, as when one dryer, or a plurality of dryers, is started or stopped. For example, this problem is reflected in the danger that lint collected in any given dryer may be blown backwardly into the heating portion of a dryer and may cause a fire or some mal-function in the dryer operation; or in the chilling of a temporarily inactive dryer by down drafts; or. in the expulsion of a blast of hot air when the basket door is opened during the cycle. The use of dampers to prevent pressure blowback in dryers is, of course, well known, but, so far as we are aware, such dampers have not been employedin dryers also having a safety control element in the form of an air-switch as taught by the present invention and wherein the blower runs continuously during the prescribed cycle of dryer operation, and wherein lint collection takes place in advance of that blower. V

, It is a purpose of the invention, therefore, to overcome the'difficulties normally found in operation of a battery of dryers connected to a common exhaust vent conduit, by use of simple and reliable safety controls. for that battery of dryers while permitting a maximum of flexibility of use for each dryer.

An object of the invention is to provide an improved combination of a plurality of clothes dryers, each including a blower which operates continuously throughout the drying cycle, and an individual exhaust. damper responsive to operation of the blower- Another object is to provide an improved damper pivotable along a thin edge pivot line.

Other objects and advantages of the invention will become more apparent as the description proceedsand when considered in conjunction with the accompanying drawings, in which FIG. 1 is a diagrammatic view showingthe combination of a plurality of dryers in accordance with the invention.

FIG. 2 is a perspective view of a dryer such as indicated in FIG. 1 and as seen from the front and with the lint tray door and the access door to the heater shown in .ments, and with the basket removed therefrom.

FIG. is a perspective view of a portion of the interior of the dryer casing of FIG. 4 as seen from the rear.

operation of the dryer.

FIG. 6 is a wiring diagram of the circuit for the dryer and suitable for coin-meter control operation.

FIG. 7 is avertical sectional view of an air switch assembly suitable for use in the circuit shown in FIG. 6 andtaken on line 77 of FIG. 8.

FIG. 8 is a sectional view taken on line 88 of FIG. 7.

FIG. 9 is a face view of the rear of a shield used in combination with the air switch assembly.

FIG. 10 is sectional view taken on line 1010 of FIG. 2 and showing the blower, exhaust pipe, and damperin dotted lines.

FIG. 11 is a partial elevation view taken on line 11-11 of FIG. 10 showing the mounting of the damper.

FIG. 12 is a plan view of the damper mounting framework.

FIG. 13 is a side elevation view showing the damper mounted in its framework and in opened position and to a somewhat larger scale, and

FIG. 14 is a schematic view showing the elements of FIG. 6 in operative relationship to each other.

In accordance with the invention there is provided a plurality of clothes dryers connected through individual exhaust pipes to a common large vent conduit. Eachdryer has .a basket compartment with an access door, and an air intake compartment and an air collecting compartment in communication with the basket compartment for permitting air circulation through the casing. A second motor drives a blower for exhausting air from the collecting compartment and located in this same compartment is a lint collector through which air leaving the basket compartment is compelled to pass. A separateaccess door is mounted in the air collecting compartment in order to provide for insertion and removal of the lint collector, and a separate first motor drives the basket. In the exhaust pipe, an improved damper is mounted adjacent the tips of the blower vanes and is adapted to occupy a normal first position closing the exhaust pipe when the blower is idle and to move to a second position opening that exhaust pipe when the blower is operating. Preferably, the sub-atmospheric pressure induced in the casing by the blower during normal operationacts upon a pressure-responsive device also responsive to pressure of the ambient air outside thecasingand causes the device to control a switch in an electrical circuit and to exert a safety control on the cycle of The electrical circuit isso arranged that the blower operates continuously throughout the cycle as selected by the operator, even though other dryers in the assembly are being started or stopped, or pressure within the dryer casing is being varied as by opening of the access doors, or by collection of lint.

Referring first to FIG. 1, a plurality of dryers such as shown at 10 are each separately connected tov a relatively large common exhaust vent conduit 11 terminating in a conventional stack section 12. As shown by dotted lines, the battery of dryers may be readily increased in number after an initial installation is made merely by providing sufiicient capacity in the vent conduit and stack. As best seen in FIG. 2, each dryer includes a casing of generally rectangular parallepiped shape having side walls 13 and 14, a rear wall 15, and a bottom 16, but is open at the top. A front panel 17 having an aperture therein adapted to be closed; by the'basket access door 18 is mounted at the central portion of the front of the casing. Openings above and below the front panel are selectively closed bythe air intake compartment access door '19 equipped with an adjustable latch arm 20, and by the collecting compartment access door 21, respectively.

bottoms by a space '25- serving to define a central'compartment for containing the dryer basket 26. It will be understood that these sweep sheets are affixed to the rear wall 15 and have upper shelves 27 and 28, which, when the front panel 17 is in place, causes all air moving from the upper air intake compartment to the air collecting compartment to move through the basket compartment. Although various forms of baskets may be employed, we prefer to use a dryer basket such as shown by Richterkessing and Ingold, Patent 2,816,742 and having a reinforced perforated cylindrical wall 30, an irnperforate rear wall 31, and a drive shaft 3-2 extending from that basket rear wall. This drive shaft extends through an aperture 33 in the rear wall of the casing and is driven by a first or basket motor 34 through a gear reducer 35. In addition, the basket rear wall 31 is spaced a suitable distance from the inner surface of the rear wali 15* of the casing to permit some air passing through the basket compartment to sweep along the rear Wall of the casing and across an aperture 36 in that portion of the rear wall of the casing located in the basket compartment.

The basket access door is suitably hinged at 37 and may have an arm 38 adapted to open a switch 39 (FIG. 4) mounted in the casing adjacent side wall 13', whenever the door is opened. Mounted within the rear and lower portions of the air collecting compartment is .a blower 40 having a central intake and a peripheral exhaust pipe 41 of generally rectangular cross section. As best seen in FIGS. 11 and 12, the exhaust pipe is located within the dryer casing and has a round lateral section 42 extending outwardly of the casing. A connecting pipe section 43 (FIG. 1) extends from the lateral section to a common exhaust vent conduit 11.

As a significant feature of the invention, an improved damper means is mounted within the discharge pipe as best seen in FIGS. 10 to 13. This damper may conveniently include a mounting framework having spaced walls 50, 51, 52 and 53 peripherally surrounding and terminating at inwardly disposed seats 54, 55, '6 and 57, respectively, located on the downstream side of the framework and enclosing an aperture between the seats. Extending on a diagonal through both the wall 53 and seat 57 are one or more sets of apertures adapted to receive a fastening means such as conventional cotter pins 58. These pins in turn extend through apertures in a damper element which may comprise a flat imperforate plate 60 having a dimension causing each of the plate edges to rest upon the seats of the framework while the damper is in closed position. The described mounting of the damper upon its framework is such that the damper pivots along a straight edge formed by the intersection of the wall 53 and seat 57 thus providing in effect a knife edge fulcrum making the damper especially responsive to changes in air pressure conditions Within the exhaust pipe. As best seen in FIG. 11, the damper and its framework are mounted in the exhaust pipe adjacent the trajectory 61 of the tips of the blower vanes and arranged so that all air driven outwardly by the blower into the exhaust pipe -'will pass through the aperture in the mounting framework for that damper. In addition, the framework is so mounted within the exhaust pipe that gravity serves to hold the damper closed when the blower is idle, but when the blower is operating, the. pressure of the outgoing air serves to raise the damper to the upper position shown in FIG. 11.

The blower, moreover, is driven by a second motor 65 and as a feature of the invention runs continuously throughout the dryer cycle after that cycle is once begun. The air moving capacity of this blower, as driven by motor 65, is so chosen, however, that when either or both of the access doors 19' and 21 are open, the blower will be unable to maintain a sufliciently low pressure within the basket compartment to prevent the air switch, later to be described, from opening certain circuits. It

be understood that at all times, however, when the blower is operating the above-described damper 60 is lifted from its seat on the framework.

By means of rigid supports interiorly of the casing and extending from the front to rear of that casing, a removable lint tray or collector 66 is mounted in the air collecting compartment beneath space 25-. This lint collec tor, as more fully shown and described in the co-pending application of Frank H. Richterkessing, Serial No. 841,3 ll filed September 21, 1959, is adapted for partial or complete withdrawal from the casing whenever desired, as for cleaning purposes or for retrieving articles that may escape the basket during a drying cycle.

The access door 21, pivotally mounted on the front of the casing beneath the front panel 17, serves to define a portion of the air collecting compartment when in normal closed position and thereby to limit the volume of air handled by the blower substantially to that amount which has passed through the basket compartment. As will later appear, if this access door 21 is advertent-ly or purposely opened during the operation of the dryer, an abnormal operating condition will occur and for which the present invention provides suitable safety precautions.

Within the confines of the casing above the shelves 27 and 28, an appreciable space, defining an air intake compartment, is formed and centrally mounted within this space is a framework 68 above which a heat insulating plate 69 may be disposed. Carried by this framework is a pair of gas burners 70 and 71 having a gas supply line leading thereto and with a solenoid-operated valve 72 in that line for controlling the supply of fuel to the burners. Air pulled into the air intake compartment through the open top of the casing, serving as an air inlet 73, moves into one end of the gas burners and upon being heated, is then pulled through space 24 into the top of the basket compartment. A suitable temperature limiting thermostat 74 subject to the heat from the drying air, is set to actuate a switch and to cut off the fuel supply when a prescribed temperature of the heated air, for example 300 F., is exceeded. In addition, a temperature regulating thermostat 75, mounted in a wiring duct 76 at the rear of the casing and having a temperature sensitive bulb 77 downstream from damper 60 and acted upon by the temperature of the exhaust air, serves to actuate a switch and to open the heating circuit in case the temerature of that exhaust air is too high as caused, for ex ample, by an excess of heat for a small load of clothes.

Referring now to FIGS. 7 to 9, a pressure-responsive means including a shield therefor and which is adapted for use with. the above-described structure, is shown. One convenient form of this pressure-responsive means comprises a pivoted damper having a lower planar portion 80 adapted when in a first position to substantially close the aperture 36 in the rear wall of the casing and when in a second and normal position to open that aperture. Olfset from the plane of portion 80 is a switch actuating arm 81 and with the damper being pivotally mounted upon a pin 8-2 intermediate the planar portion and arm and supported upon a bracket 83. This bracket in turn is supported upon a back plate assembly having a plate 84 adapted for mounting flush against the back wall 15 of the dryer casing. The back plate contains an aperture 85 coinciding with the aperture 36 of the casing and also has an upper-shelf 86 and a lower shelf 87 extending normally from the plane of the back plate. The upper and lower shelves are of equal width but the lower shelf is shorter in length than the upper shelf, thus to provide an opening 88 (FIG. 7). Carried by the bracket is a micro-switch assembly 89 having a resilient arm 90 held at all times in engagement with the switch-actuating arm 81 of the damper and arranged to close that switch when arm 81 moves to the position at which the damper closes the apertures 36 and 85. For convenience, switch 89' is herein termed an air switch.

Due tothe combined effects of the offset portions of the damper, the location of the greater mass of the damper below pivot pin 82, and the action of resilient arm 90; the normal position of the damper is generally as seen in FIG. 7. To limit the outward swing of the damper and at the same time to assist in calibrating the entire pressure-responsive means, a suitable bracket 91 having an abutment 92 against which the damper rests in normal position, is rigidly aflixed to the shelf 87 of the back plate assembly.

Since operation of the air switch should be reliable in all respects, a shield is provided to assure that reliability in operation. One convenient form of shield may comprise a partial box-like member having a front plate 93 with a plurality of apertures 94, 95 and 96 therein in confronting relation to the planar portion of damper 80. At its lower edge the front plate may be secured to one end of the bracket 91 and at its upper edge the front plate may overlie the edge of the upper shelf as seen at 9'7. The box-like shield member also includes sides 98 and 99 extending to the surface of the back plate 84. With the pressure-sensitive air switch thus assembled, ambient air whose pressure is a factor in the operation of the switch, can contact the damper surface only by moving into the box-like structure through the lower opening 8 8 and through the confronting apertures 94, 95 and 96. As will be apparent, the described shield also serves as a mechanical shield against inadvertent striking of the damper.

In general, the size and speed of blower 40 is such that during normal operation of the dryer a vacuum reading of about 0.15 to 0.30 inch of water column, read against the pressure of the outside ambient air, is maintained within the dryer basket compartment due to the rate of removal of air from that compartment by that blower. Under these conditions, the planar portion 80 of the damper seats positively in its first or closed position covering the apertures 36 and 85 and most importantly, does not teeter or adopt an intermediate position as it moves from its open to its closed position at the start of the drying operation. The presence of the apertures in the front plate of the shield are found to contribute to this positive closing movement of the damper. Moreover, when the difference in pressure between the air in the basket compartment and the ambient air drops to a prescribed value, for example, 0.09 inch of Water column, the damper being biased toward its open or second position, as above-described, moves positively to that position and comes to rest against abutment 92.

With the foregoing in mind, reference now is made to FIG. 6 showing an across-the-line electrical circuit for the dryer; to FIG. 14 showing a schematic arrangement of the mechanical and electrical elements; and to the following description of the operation of the dryer in accordance with the invention.

When a coin is deposited in slot 100, or when an alternative manual starting means is used, a starting switch 101 is first closed whereupon a timing circuit is made from conductor 102 through the closed starting switch, timer motor 103, and conductor 104 to return conductor 105. If desired, an arrangement including a time switch may be employed with the starting switch, and which may be of a conventional type having the ability to permit untimed operation as when the dryness of the load of clothes in the basket is judged by inspection or by operation of a temperature signal light. Since this type of control is well known and forms no part of the present invention, it has been omitted from the drawings in the interests of simplicity. In general then, the above-described timing circuit is maintained until the end of a prescribed drying cycle or until the operator wishes to terminate the drying cycle.

Closing of the timing circuit also establishes a relay circuit through starting switch 101, conductor 106, relay 5 107, conductor 108, and return conductor 105. As relay 107 closes, it in turn establishes a blower circuit through conductor 102., conductor 109, relay contacts 110, conductor 111, motor 65 and return conductor 105, and this circuit remainsclosed as long as the timing circuit is closed.

Thus, it will be seen that when the blower circuit is closed, motor 65 begins to drive blower 40 and that the damper 60 in the exhaust pipe is immediately opened giving communication to the common vent conduit 11. Prior to this opening of damper 60, pressure blow backs from other dryers of the battery into this particular dryer cannot occur nor could cold air which might cause undesired condensation within this particular dryer, enter into the dryer. After blower 40 once begins to operate, these conditions cannot, of course, occur, even though damper 60 is open.

Furthermore, as blower 40 begins its operation it then eifects a sub-atmospheric pressure within the basket compartment tending to move the pressure-sensitive air switch to closed position. The continuous driving of the blower, in addition, is important in that if the basket door 18 is opened during the dryer cycle, no hot air blast is blown toward the operator; the dryer area is kept cooler for the operator if he wishes to handle the clothes while the timer is still operating; and free access at all times to the lint collector is in no way impeded.

Simultaneously with the closing of the blower circuit, relay contacts 112 also close. If at this time the basket door 18 is closed, and if the lint tray is sufficiently clean, and if the lint tray access door 21 is closed, the rate of removal of air from the basket compartment by the blower will be sufficient to create the above-mentioned pressure differential acting upon damper 80 and thus the switch 89 will also close. At the beginning of operation, the thermostatically controlled switches 74 and 75 will, of course, be closed, since the burners have not yet attained their full heating effect. Accordingly under these normal conditions, closing of relay contacts 112 establishes a heating circuit through conductor i113, door switch 39, conductor 114, closed air switch 89, conductor 115, temperature regulating thermostat switch 74, conductor 116, temperature limiting thermostat switch 75, conductor 117, solenoid valve 72, conductor 118, and return conductor 105.

As this circuit is completed, the valve 72 is openedand fuel is supplied to the burners whereupon heated air is normally until the timing circuit is opened.

Simultaneously with the closing of air switch 89, a shunt 'circuit is made through conductor 119, motor 34, driving basket 26, conductor .120, and return conductor 105. As

this circuit is closed, the clothes in the basket are tumbled in the presence of the hot air being drawn through the hasket compartment. However, in the event that the basket access door 18 is opened, or if the air switch is openedfor any reason, the basket will come to rest as this circuit is interrupted. It will be understood that wide ranges in loads of clothes to be dried, both as to weight and type of fabric, will be encountered in the use of the invention in unattended dryer establishments. In some cases, the heat supply may be cut off temporarily either because excess heat is being supplied, or because the temperature of the exhaust is too high, thus causing an interruption of only a temporary nature in the above described circuit. For such a temporary interruption there is no need to bring the basket to rest and in fact for certain fabrics it is better to have them continue to tumble rather than to rest in contact with heated metallic surfaces of the basket. The invention accordingly provides for the basket motor to continue its rotation while either or both of the thermostat switches 74 and 75 are open, provided of course that the blower 40 is still operating and the switches 39 and 89 Having thus described the invention, it is intended to cover by the appended claims all such modifications or variations as fall within the true spirit and scope of the invention.

What is claimed is:

1. An assembly of independently operable, automatically controlled, clothes dryers comprising in combination, a plurality of dryers having a common exhaust vent conduit; each of said dryers including a casing having a basket compartment serving as a drying chamber, an air intake compartment, and an air collecting compartment in communication respectively with said basket compartment and permitting air circulation through said casing, an inlet for air into said air intake compartment, so-lenoid-actuated means for heating air supplied into said intake compartment, means including an exhaust pipe and blower for exhausing air from said collecting compartment into said vent conduit and for establishing a subatmospheric pressure in said casing commensurate with the rate of removal of air therefrom, said blower being adapted to draw air from said air inlet to said heating means and thence to said drying chamber, a basket in said basket compartment, a first motor driving said basket, means responsive to the difference in pressure between the interior of said casing and the ambient air exterior of said casing, and movable in response to said pressure difference between a first circuitaclosing position and a second circuit-opening position, a second motor for driving said blower, and a damper in said exhaust pipe downstream from said blower and normally occupying a first position closing said exhaust pipe from said common vent conduit when said blower is idle and movable to a second position opening said exhaust pipe to said common vent conduit when said blower is operating and exerting its influence upon said pressure-responsive means, an electrical circuit including a starting means, adapted when operated, to establish jointly separate circuits through said solenoid-actuated heating means, said first motor, and said second motor respectively, and a switch actuated by said pressure-responsive means and located in the circuits between said starting means and said solenoid actuated heating means, and said first motor respectively, whereby upon movement of said pressure-responsive means to its first position, said separate circuits to said first motor and to said solenoid-actuated heating means are established without interruption to said separate circuit through said second, motor and upon movement of said pressure-responsive means to its second position, said separate circuits to said first motor and to said solenoid-actuated heating means are interrupted without interruption of said separate circuit through said second motor.

2. Apparatus as defined in claim 1 wherein each of said dryers includes a door in said basket compartment permitting selective access to said basket, and a door-actuated switch in said electrical circuit, said-door -actuated switch being located in said circuit between said starting means and said solenoid-actuated heating means and said first motor whereby upon opening of said door-actuated switch said separate circuits to said first motor and to said solenoid-actuated heating means are interrupted without interruption of said separate circuit to said second motor,

3. Apparatus as defined in claim 1 wherein each of said dryers includes a temperature limiting control means responsive to the temperature of the air leaving said air intake compartment and adapted to actuate a switch disposed in said separate circuit between said starting means and said solenoid-actuating heating means whereby upon opening of said last-mentioned switch said heating means may be inactivated without interruption of said separate circuits to said first motor and to said second motor, respectively.

4. Apparatus as defined in claim 1 wherein each of said dryers includes a temperature regulating control means responsive to the temperature of the gases leaving said air collecting chamber and adapted to actuate a switch disposed in said separate circuit between said starting means and said solenoid-actuated heating means whereby upon opening of said last-mentioned switch said heating means may be inactivated without interruption of said separate circuits to said first motor and to said second motor, respectively.

5. Apparatus as defined in claim 1 wherein said damper comprises an impenforate, fiat member pivotally mounted along one edge upon a framework wholly enclosed within said exhaust pipe and having means securing said damper along said one edge thereof to said framework for pivotal movement of the same between said first and secondpositions occupied by the same.

6. Apparatus as defined in claim 1 wherein each of said dryers includes a separate door in said air collecting compartment permitting selective access to a lint collector therein, said separate door being movable between a first position closing said air collecting compartment and permitting said blower to exert its influence upon said pressure-responsive means and a second position openingsaid .air collecting compartment and preventing said blower from exerting its influence on said pressure-responsive means.

References Cited in the file of this patent UNITED STATES PATENTS 1,702,968 Heinrich Feb. 19, 1929 2,604,313 Grantham July 22, 1952 2,750,869 Cole et al June 19, 1956 2,754,748 Daggett July 17, 1956 2,800,853 Spear July 30, 1957 2,825,148 Olson Mar. 4, 1958 

